6.3 KiB
6.3 KiB
id | challengeType | forumTopicId | title |
---|---|---|---|
5a24c314108439a4d4036144 | 6 | 301435 | 使用 Provider 连接 Redux 和 React |
Description
react-redux
包可帮助我们完成这些任务。
React Redux 提供的 API 有两个关键的功能:Provider
和connect
。你会在另一个挑战中学connect
。Provider
是 React Redux 包装 React 应用的 wrapper 组件,它允许你访问整个组件树中的 Reduxstore
及dispatch(分发)
方法。Provider
需要两个 props:Redux store 和 APP 应用的子组件。用于 APP 组件的Provider
可这样定义:
<Provider store={store}>
<App/>
</Provider>
Instructions
DisplayMessages
组件。新出现的代码是底部的AppWrapper
组件,这个顶级组件可用于渲染ReactRedux
的Provider
,并把 Redux 的 store 作为 props 传入。接着,渲染DisplayMessages
为子组件。完成这些任务后,你会看到 React 组件渲染到页面上。
注意: React Redux 在此可作全局变量,因此你可通过点号表示法访问 Provider。利用这一点,编辑器上的代码把Provider
设置为常量,便于你在AppWrapper
渲染方法中使用。
Tests
tests:
- text: <code>AppWrapper</code>应渲染。
testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('AppWrapper').length === 1; })());
- text: <code>Provider</code>组件应传入相当于 Redux store 的<code>store</code>参数。
testString: getUserInput => assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return getUserInput('index').replace(/\s/g,'').includes('<Providerstore={store}>'); })());
- text: <code>DisplayMessages</code>应渲染为<code>AppWrapper</code>的子组件。
testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('AppWrapper').find('DisplayMessages').length === 1; })());
- text: <code>DisplayMessages</code>组件应渲染 h2、input、button、<code>ul</code>四个元素。
testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('div').length === 1 && mockedComponent.find('h2').length === 1 && mockedComponent.find('button').length === 1 && mockedComponent.find('ul').length === 1; })());
Challenge Seed
// Redux 代码:
const ADD = 'ADD';
const addMessage = (message) => {
return {
type: ADD,
message
}
};
const messageReducer = (state = [], action) => {
switch (action.type) {
case ADD:
return [
...state,
action.message
];
default:
return state;
}
};
const store = Redux.createStore(messageReducer);
// React 代码:
class DisplayMessages extends React.Component {
constructor(props) {
super(props);
this.state = {
input: '',
messages: []
}
this.handleChange = this.handleChange.bind(this);
this.submitMessage = this.submitMessage.bind(this);
}
handleChange(event) {
this.setState({
input: event.target.value
});
}
submitMessage() {
const currentMessage = this.state.input;
this.setState({
input: '',
messages: this.state.messages.concat(currentMessage)
});
}
render() {
return (
<div>
<h2>Type in a new Message:</h2>
<input
value={this.state.input}
onChange={this.handleChange}/><br/>
<button onClick={this.submitMessage}>Submit</button>
<ul>
{this.state.messages.map( (message, idx) => {
return (
<li key={idx}>{message}</li>
)
})
}
</ul>
</div>
);
}
};
const Provider = ReactRedux.Provider;
class AppWrapper extends React.Component {
// 在此渲染 Provider
// 请在本行以上添加你的代码
};
After Test
ReactDOM.render(<AppWrapper />, document.getElementById('root'))
Solution
// Redux Code:
const ADD = 'ADD';
const addMessage = (message) => {
return {
type: ADD,
message
}
};
const messageReducer = (state = [], action) => {
switch (action.type) {
case ADD:
return [
...state,
action.message
];
default:
return state;
}
};
const store = Redux.createStore(messageReducer);
// React Code:
class DisplayMessages extends React.Component {
constructor(props) {
super(props);
this.state = {
input: '',
messages: []
}
this.handleChange = this.handleChange.bind(this);
this.submitMessage = this.submitMessage.bind(this);
}
handleChange(event) {
this.setState({
input: event.target.value
});
}
submitMessage() {
const currentMessage = this.state.input;
this.setState({
input: '',
messages: this.state.messages.concat(currentMessage)
});
}
render() {
return (
<div>
<h2>Type in a new Message:</h2>
<input
value={this.state.input}
onChange={this.handleChange}/><br/>
<button onClick={this.submitMessage}>Submit</button>
<ul>
{this.state.messages.map( (message, idx) => {
return (
<li key={idx}>{message}</li>
)
})
}
</ul>
</div>
);
}
};
const Provider = ReactRedux.Provider;
class AppWrapper extends React.Component {
// change code below this line
render() {
return (
<Provider store = {store}>
<DisplayMessages/>
</Provider>
);
}
// change code above this line
};